A steady‐state and time‐resolved fluorescence, circular dichroism study on the binding of myricetin to bovine serum albumin

Abstract

The binding mechanism of myricetin (Myr) to bovine serum albumin was investigated by using steady-state and time-resolved fluorescence and circular dichroism. The results of the steady-state fluorescence quenching experiment indicate that it is a static quenching process (C(Myr)/C(BSA) < or = 3) at low quencher concentration and the binding site is located near the Trp212 residue. The association constants at the different temperatures were calculated. From the thermodynamic parameters, enthalpy change (DeltaH(0)), Gibbs free energy change (DeltaG(0)) and entropy change (DeltaS(0)) obtained in the experiment, it was found that hydrophobic and electrostatic interactions play important roles in binding Myr to BSA. According to the Föster energy transfer theory, the separation distance, r, the energy transfer efficiency, E, and Föster radius, R(0), were calculated. The results obtained from the above experiments indicate that Myr can be tightly bound to BSA. Then, the effects of ionic strength, metal ion, pH and surfactants on the binding Myr and BSA were investigated, which also showed that electrostatic and hydrophobic interactions play a major role in the association process. On the other hand, the conformation and secondary structure of BSA were further studied through circular dichroism and fluorescence synchronous spectra. It was found that the conformation and secondary structure of BSA had also changed after interaction with Myr. The time-resolved fluorescence study showed that the short lifetime of BSA decreased after the addition of Myr, which implies that the buried Trp 212 is the main binding site.

Spectrophotometric studies on the interaction between myricetin and lysozyme in the absence or presence of Cu2+or Fe3+

“…3 (Table 1) are 3 orders of magnitude greater than the maximum diffusion collision quenching rate constant (2.0 Â 10 10 L mol À 1 s À 1 ) of a variety of quenchers with biopolymer [15]. Therefore, the fluorescence quenching of Lys by myricetin with or without Cu 2 + or Fe 3 + should be resulting from static quenching mechanism owing to a complex formation rather than a dynamic quenching mechanism at low concentrations ([myricetin]/[Lys]o2.2) of myricetin, which is in accordance with the quenching mechanism of HSA or BSA by myricetin studied in the previous literature [16,17].…”

“…Therefore, the reduction of K and n may result from the competition of metal ions and myricetin at higher concentrations of myricetin. However, it also can be observed that the binding constant of myricetin-Lys complex is a little larger than that of myricetin-HSA complex or myricetin-BSA complex [16,17]. This result may arise from the stronger hydrophobic forces between the aromatic ring of myricetin and the hydrophobic amino acid residues of Lys.…”

Role of the Flavan-3-ol and Galloyl Moieties in the Interaction of (−)-Epigallocatechin Gallate with Serum Albumin

“…30,31 EGCg substantially diminished the fluorescence lifetime of Trp 213 in a pH-dependent fashion, reducing the lifetime by about 50% at pH 5.0 or 7.4 (Table 2). At the same pH values, EGCg diminished the fluorescence lifetime of Trp 134 about 15–25% (Table 2).…”

Spectroscopic and molecular modelling analysis of the interaction between ethane‐1,2‐diyl bis(N,N‐dimethyl‐N‐hexadecylammoniumacetoxy)dichloride and bovine serum albumin

“…The instrumental response function was recorded sequentially using a scattering solution and a time calibration of 114 ps/channel. Data were analysed using a sum of exponentials, employing a non‐linear least squares reconvolution analysis from Horiba (Jobin Yvon, IBH Ltd), of the form : where τ i are the decay times, a i is the amplitude of the components at t = 0 and n is the number of decay times.…”